Communication frequency spectrum is often scarce with precious little available for future technologies. Most of the world's available frequency bands have already been allocated to specific services. What remains is auctioned by government agencies typically for billions of dollars.
From a mobile operator's perspective, effective delivery of services to customers is dependent upon maximizing both network capacity and coverage. Network capacity is improved by enabling more non-interfering users within a base station cell or providing higher bandwidth to users within range of a base station. Thus, each new generation of communications systems design attempts to provide additional capacity based on technological advances in the field.
Nevertheless, high data-rate wireless access is demanded by many applications. Traditionally, more bandwidth is required for higher data-rate transmission. However, due to spectral limitations, it is often impractical or sometimes very expensive to increase bandwidth. In such cases, Multiple-Input Multiple-Output (MIMO) systems using multiple transmit and receive antennae provide an alternative solution (See, David Gesbert, Mansoor Shan, Da shan Shiu, Peter J. Smith, and Ayman Naguib, “From Theory to Practice: an Overview of MIMO Space-Time Coded Wireless Systems,” IEEE Journal on Selected Areas in Communications, vol. 21, no. 3, pp. 281-302, April 2003). In particular, Orthogonal Frequency Division Multiplexing (OFDM) can be used in conjunction with MIMO (See, Richard D. J. van Nee and Ramjee Prasad, Eds., OFDM for Wireless Multimedia Communications, Artech House Publishers. Norwood, Mass. 02062, U.S.A., 2000). A MIMO-OFDM system can significantly improve the link reliability and throughput of wireless communication systems (See, Helmut Bolcskei, Principles of MIMO-OFDM Wireless Systems, 2004. David Perels, Simon Haene, Peter Luethi, Andreas Burg, Norbert Felber, Wolfgang Fichtner, and Helmut Bolcskei, “ASIC Implementation of a MIMO-OFDM Transceiver for 192 Mbps WLANs,” European Solid-State Circuits Conference (ESSCIRC 05), pp. 215-218, September 2005). These gains come at no additional transmit power or bandwidth expenditure.
However, one of the main obstacles in implementing MIMO-OFDM is the extremely high computational requirements. For this reason, software implementation within the terminal stations is very difficult to achieve and only custom hardware solutions are conventionally available (See, John C. Glossner, Erdem Hokenek, and Mayan Moudgill, “Multithreaded Processor for Software Defined Radio,” Proceedings of the 2002 Software Defined Radio Technical C” San Diego, Calif., November 2002, vol. 1, pp. 195-199).